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; test source file for assembling to ELF shared library
; build with:
; nasm -f elf elfso.asm
; ld -shared -o elfso.so elfso.o
; test with:
; gcc -o elfso elftest.c ./elfso.so
; ./elfso
; (assuming your gcc is ELF, and you're running bash)
; This file should test the following:
; [1] Define and export a global text-section symbol
; [2] Define and export a global data-section symbol
; [3] Define and export a global BSS-section symbol
; [4] Define a non-global text-section symbol
; [5] Define a non-global data-section symbol
; [6] Define a non-global BSS-section symbol
; [7] Define a COMMON symbol
; [8] Define a NASM local label
; [9] Reference a NASM local label
; [10] Import an external symbol
; [11] Make a PC-relative call to an external symbol
; [12] Reference a text-section symbol in the text section
; [13] Reference a data-section symbol in the text section
; [14] Reference a BSS-section symbol in the text section
; [15] Reference a text-section symbol in the data section
; [16] Reference a data-section symbol in the data section
; [17] Reference a BSS-section symbol in the data section
BITS 32
GLOBAL lrotate:function ; [1]
GLOBAL greet:function ; [1]
GLOBAL asmstr:data asmstr.end-asmstr ; [2]
GLOBAL textptr:data 4 ; [2]
GLOBAL selfptr:data 4 ; [2]
GLOBAL integer:data 4 ; [3]
EXTERN printf ; [10]
COMMON commvar 4:4 ; [7]
EXTERN _GLOBAL_OFFSET_TABLE_
SECTION .text
; prototype: long lrotate(long x, int num);
lrotate: ; [1]
push ebp
mov ebp,esp
mov eax,[ebp+8]
mov ecx,[ebp+12]
.label rol eax,1 ; [4] [8]
loop .label ; [9] [12]
mov esp,ebp
pop ebp
ret
; prototype: void greet(void);
greet push ebx ; we'll use EBX for GOT, so save it
call .getgot
.getgot: pop ebx
add ebx,_GLOBAL_OFFSET_TABLE_ + $$ - .getgot wrt ..gotpc
mov eax,[ebx+integer wrt ..got] ; [14]
mov eax,[eax]
inc eax
mov [ebx+localint wrt ..gotoff],eax ; [14]
mov eax,[ebx+commvar wrt ..got]
push dword [eax]
mov eax,[ebx+localptr wrt ..gotoff] ; [13]
push dword [eax]
mov eax,[ebx+integer wrt ..got] ; [1] [14]
push dword [eax]
lea eax,[ebx+printfstr wrt ..gotoff]
push eax ; [13]
call printf wrt ..plt ; [11]
add esp,16
pop ebx
ret
SECTION .data
; a string
asmstr db 'hello, world', 0 ; [2]
.end
; a string for Printf
printfstr db "integer==%d, localint==%d, commvar=%d"
db 10, 0
; some pointers
localptr dd localint ; [5] [17]
textptr dd greet wrt ..sym ; [15]
selfptr dd selfptr wrt ..sym ; [16]
SECTION .bss
; an integer
integer resd 1 ; [3]
; a local integer
localint resd 1 ; [6]
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